Enter Your Email Address to Receive a
Copy of MedicExhange Member Demograhpics

An MRI protocol for carotid plaque delivered a more clinically relevant risk assessment for coronary artery disease.

Using this protocol, Teruo Noguchi, MD, of the National Cerebral and Cardiovascular Center in Suita, Japan, and colleagues identified the presence of high-intensity plaque as the strongest independent predictor of cardiac events.

For this study, reported in the July issue of the Journal of the American College of Cardiology, Noguchi's group used magnetization-prepared rapid acquisition with gradient echo (MPRAGE) MRI to observe high-intensity signals in carotid plaques to determine if the presence of these signals was associated with cardiac events.They looked at the signal intensity of carotid plaques in 217 patients with clinically stable coronary artery disease (CAD) using the MPRAGE MRI technique.

They defined stable CAD as the absence of episodes of angina at rest on admission in patients with angiographically documented stenosis of greater than 50% in at least one of the major coronary arteries.

IMT measurement was conducted for all patients via ultrasonography with a 7.5 MHz linear-array transducer prior to MR imaging on a 1.5-tesla unit with standard neck and spine array coils.

The MPRAGE protocol is a noncontrast, T1-weighted, inversion recovery-based 3-D imaging technique. Gadolinium-enhanced, multislab, 3-D time-of-flight MR angiography also was performed to determine lumen shape and plaque morphology after MPRAGE imaging.

Using a 5-8 mm region of interest, a radiologist analyzed the carotid plaque signal intensity on the MPRAGE images relative to that of the adjacent muscle.

Patients with plaques in either the right or left carotid artery in which any region of the plaque exhibited a signal intensity 200% greater than the adjacent muscle were placed in the high-intensity plaque group (116 patients). The remaining 101 patients were placed in a non-high-intensity plaque group.

The high-intensity plaque group also had lower HDL cholesterol levels, more multivessel coronary artery disease, a greater history of previous MI, higher high-sensitivity C-reactive protein, and increased IMT values.

After imaging was completed, all patients were followed up at the facility for a period of 12 to 72 months, or until the occurrence of clinical coronary events including cardiac death, nonfatal acute MI, unstable angina, or unplanned hospitalization for recurrent angina. These events were grouped together as a composite outcome.

The mean follow-up time was 38.3 months. During that period, there were 31 coronary events in the high-intensity plaque group, but only five in the non-high-intensity plaque group.

Unstable angina accounted for 16 of the 31 events in the high-intensity plaque group and was the only one by itself that was statistically significant.

"The presence of high-intensity plaque was significantly associated with an increased probability of coronary events in patients with stable CAD (P<0.001 by log-rank test)," the authors wrote.

A univariate analysis of coronary risk factors, carotid ultrasound data, and MRI analysis demonstrated that maximum IMT, high-intensity plaque, multivessel CAD, high-sensitivity C-reactive protein (hsCRP) and prior MI were all significant predictors of clinical coronary events (P<0.05), according to the researchers.

Further analysis determined that the presence of high-intensity plaque "was found to be the most significant independent predictor of future coronary complications in patients with stable CAD compared with IMT (HR 1.62, 95% CI 0.97 to 2.44, P=0.055), hsCRP, previous MI, and multivessel CAD," the authors stated.

Limitations of the study included a relatively small number of patients and the fact that few patients experienced one of the primary endpoints during the study, which meant the study did not have sufficient statistical power to ascertain whether or not the new marker was superior to established risk factors, according to the investigators.

Although these results are "exciting and promising," translation of the main findings to a more general high-risk population will be challenging, wrote Chun Yuan, PhD, of the University of Washington School of Medicine in Seattle, and colleagues in an accompanying commentary.

"Prospective, serial studies with MRI will result in a better understanding of the nature and etiology of intraplaque hemorrhage, may lead to the discovery of novel therapies to prevent its development, and will be needed to assess whether such therapies lead to a reduction in coronary and carotid events," they wrote.

Source: Journal of the American College of Cardiology

See Our Directory to know about  MRI companies  and  MRI Products.